Running one voice coil on DVC sub ok?

[mr.sagat 10]

I have heard a million times that running one voice coil on a sub with multiple coils is wrong. I read an article by Adire Audio years ago and they actually suggested running on one voice coil in certain situations. I also remember that running one VC while "shorting" out the second VC would change woofer characteristics, I believe it raises QTS if I remember correctly. I understand that it would basically halve the power handling of the sub. What else does it do? The article also says something about a sub with 300 watts wasting 298 watts as heat, and only using around 2 as musical energy. Are speakers really, that inefficient?

Here's the article if some of you want a good read..

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[RaTtLz 3]

[Julian 641]

I've never heard anything wrong with doing this besides the fact it halves your RMS rating, but besides that i see nothing wrong with doing this.

[Randal Johnson 544]

[KU40 173]

There's nothing wrong with doing it, it doesn't inherently hurt the speaker. Yes it will halve the speaker's power handling, and change several of the speaker's T/S specs. And yes, woofers are that inefficient.

[kirill007 52]

Yep, no problem to use the woofer with only one coil as long as you know the Pe drops(=thermal power handling), and the Qts and a other Q parameter changes.

And you also get less motor force i think.

[Impious 1,476]

I have heard a million times that running one voice coil on a sub with multiple coils is wrong. I read an article by Adire Audio years ago and they actually suggested running on one voice coil in certain situations. I also remember that running one VC while "shorting" out the second VC would change woofer characteristics, I believe it raises QTS if I remember correctly. I understand that it would basically halve the power handling of the sub. What else does it do?

If you are only using a single coil of a DVC driver and leave the other coil open Qes and hence Qts would double, sensitivity would decrease by 3db, motor force (Bl^2/Re) is halved, the inductive corner frequency doubles and power handling is decreased (some argue that power handling is not cut completely in half because the 2nd coil helps act essentially as a heat sink which helps dissipate some of the heat, but I've never seen any testing done to confirm power handling of a single coil compared to both coils).

I found this link by accident one day a couple years ago, and it shows a good comparison of a driver's change in T/S parameters with coils wired in series, parallel, one coil driven the other shorted (for both coils), and then one coil driven and the other open (for both coils); woofertester.com

If you are interested in the math of why the above happens, you can skim through the formulas for the T/S parameters here on Wikipedia.

Resistively Damped Operation can be accomplished by only driving one coil and using a resistor or potentiometer across the 2nd coil to "change" the Q of the driver. This was the entire premise behind the old Ascendant Atlas driver.

Are speakers really, that inefficient?

Yes, they really are. If you want to calculate the efficiency of your subs (or any other speaker), you would use the formula found here;

Efficiency (N₀) = 9.64 * 10^(-10) * Fs^3 * Vas / Qes

*To express as a percent, multiply by 100

*Vas in liters

So, for example the Efficiency of a 12" SSA Icon is;

9.64 * 10^(-10) * 29.9^3 * 43.7 / 0.45 = .002502

.002502*100 = .2502%

And to verify, to convert this into SPL

112+10*log(.002502) = 85.98db

And the sensitivity of the SSA Icon according to their specs;

Spl 86.0 1W/1m

TaaDaa!!

So the SSA Icon converts .25% of the power you feed it to acoustic power, the remaining 99.75% is spent as heat.

[Julian 641]

I have heard a million times that running one voice coil on a sub with multiple coils is wrong. I read an article by Adire Audio years ago and they actually suggested running on one voice coil in certain situations. I also remember that running one VC while "shorting" out the second VC would change woofer characteristics, I believe it raises QTS if I remember correctly. I understand that it would basically halve the power handling of the sub. What else does it do?

If you are only using a single coil of a DVC driver and leave the other coil open Qes and hence Qts would double, sensitivity would decrease by 3db, motor force (Bl^2/Re) is halved, the inductive corner frequency doubles and power handling is decreased (some argue that power handling is not cut completely in half because the 2nd coil helps act essentially as a heat sink which helps dissipate some of the heat, but I've never seen any testing done to confirm power handling of a single coil compared to both coils).

I found this link by accident one day a couple years ago, and it shows a good comparison of a driver's change in T/S parameters with coils wired in series, parallel, one coil driven the other shorted (for both coils), and then one coil driven and the other open (for both coils); woofertester.com

If you are interested in the math of why the above happens, you can skim through the formulas for the T/S parameters here on Wikipedia.

Resistively Damped Operation can be accomplished by only driving one coil and using a resistor or potentiometer across the 2nd coil to "change" the Q of the driver. This was the entire premise behind the old Ascendant Atlas driver.

Are speakers really, that inefficient?

Yes, they really are. If you want to calculate the efficiency of your subs (or any other speaker), you would use the formula found here;

Efficiency (N₀) = 9.64 * 10^(-10) * Fs^3 * Vas / Qes

*To express as a percent, multiply by 100

*Vas in liters

So, for example the Efficiency of a 12" SSA Icon is;

9.64 * 10^(-10) * 29.9^3 * 43.7 / 0.45 = .002502

.002502*100 = .2502%

And to verify, to convert this into SPL

112+10*log(.002502) = 85.98db

And the sensitivity of the SSA Icon according to their specs;

Spl 86.0 1W/1m

TaaDaa!!

So the SSA Icon converts .25% of the power you feed it to acoustic power, the remaining 99.75% is spent as heat.

That's extremely interesting Impious.

Great read, you should put this in the technical section!